CXCR1_wt ( IC50 = 5.6 nM ); CXCR1_Ile43Val ( IC50 = 80 nM ); CXCR1 ( IC50 = 1 nM ); CXCR2 ( IC50 ∼100 nM )

In vitro activity: Reparixin inhibits intracellular signal pathways without affecting receptor bindings. It is a non-competitive allosteric blocker of CXCR1 and CXCR2 receptor activation. Reparixin is a powerful and specific inhibitor of many biological activities induced by CXCL8, including the recruitment of leukocytes and functional inflammatory responses. Reparixin, however, has no effect on CXCR1/CXCR2 activation brought on by C5a, fMLP, CXCL12, or a number of other GPCR agonists. Angiotensin II receptor synthesis can be regulated by reparixin, which may have an impact on Ang II-induced hypertension[1]. Reparixin does not interfere with other receptors; instead, it selectively inhibits CXCR1/2-mediated mouse and human neutrophil migration in culture. By blocking phosphorylation of downstream signaling molecules, reparixin suppresses CXCL8-induced neutrophil activation via human CXCR1 and human CXCR2. The phagocytosis of Escherichia coli bacteria is unaffected by reparixin, but it does inhibit the rise in intracellular free calcium, the release of elastase, and the generation of reactive oxygen intermediates[2].

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- Inhibiting Neutrophil Migration and Activation: Reparixin is a non - competitive allosteric blocker of CXCR1 and CXCR2 receptor activation. It can specifically block CXCR1/2 - mediated mouse and human neutrophil migration in vitro. It inhibits CXCL8 - induced neutrophil activation through human CXCR1 and CXCR2, blocking the phosphorylation of downstream signalling molecules. It also prevents the increase of intracellular free calcium, elastase release and production of reactive oxygen intermediates, while not affecting the phagocytosis of Escherichia coli bacteria [1, 3]

Reparixin reduces inflammatory responses in a variety of injury models by inhibiting the activation of the CXCL8 receptors, CXCR1 and CXCR2. Reparixin increases blood flow and effectively lowers systolic blood pressure. Comparing SHR-R (the reparixin-treated group) to SHR-N (the regular saline-treated SHR), the thoracic aorta wall thickness is significantly lower in the former[1]. Rats with spontaneous hypertension (SHR).

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Reparixin, an inhibitor of CXCL8 receptor CXCR1 and CXCR2 activation, has been shown to attenuate inflammatory responses in various injury models. In the present study, the hypertension-related functional roles of reparixin were examined in hypertensive animals. Spontaneously hypertensive rats (SHR) at the age of 18 weeks were administered a subcutaneous injection of reparixin (5 mg/kg) daily for 3 weeks (SHR-R, n=5). Control groups consisted of normal saline-treated SHR (SHR-N, n=5) and normotensive Wistar-Kyoto rats (WKY-N, n=5). Reparixin effectively decreased systolic blood pressure and increased the blood flow. The thoracic aorta wall thickness was significantly decreased in SHR-R compared to SHR-N. Expressions of CXCL8, CCL2, 12-lipoxygenase (LO) and endothelin (ET)-1 were significantly decreased in SHR-R thoracic aorta tissues compared to SHR-N. Furthermore, expression of angiotensin II subtype I receptor (AT(1)R) protein was decreased in SHR-R thoracic aorta tissues compared to SHR-N. In addition, the plasma levels of nitric oxide were slightly elevated in SHR-R compared to the levels in SHR-N. These findings indicate that inhibition of hypertension-related mediators by reparixin results in the reduction of blood pressure in SHR. Therefore, these results suggest that reparixin-mediated blockade of CXCL8 receptor activation attenuates vascular hypertension in SHR.[1]

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Pharmacological inhibition of CXCR2 by Reparixin reduced CXCL1-induced leukocyte arrest in the microcirculation of the cremaster muscle, but did not influence arrest in response to leukotriene B4 (LTB4) demonstrating specificity. Reparixin (15 microg g(-1)) reduced neutrophil recruitment in the lung by approximately 50% in a model of LPS-induced ALI. A higher dose did not provide additional reduction of neutrophil recruitment. This dose also reduced accumulation of neutrophils in the interstitial compartment and vascular permeability in LPS-induced ALI. Furthermore, both prophylactic and therapeutic application of Reparixin improved gas exchange, and reduced neutrophil recruitment and vascular permeability in a clinically relevant model of acid-induced ALI. Conclusions and implications: Reparixin, a non-competitive allosteric CXCR2 inhibitor attenuates ALI by reducing neutrophil recruitment and vascular permeability[2].

Reparixin L-lysine salt is a new and powerful small molecular weight allosteric inhibitor of chemokine receptor 1/2 (CXCR1/2) activation. It is the L-lysine salt form of reparixin. Reparixin, as demonstrated in particular experiments on CXCR1/L1.2 and CXCR2/L1.2 transfected cells and on human PMNs, is a strong functional inhibitor of CXCL8-induced biological activities on human PMNs with a marked selectivity (about 400-fold) for CXCR1. Reparixin's effectiveness is considerably reduced in L1.2 cells that express the CXCR1 Ile43Val mutant (IC50 values for CXCR1 wt and CXCR1 Ile43Val, respectively, are 5.6 nM and 80 nM).

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- Attenuating Inflammatory Responses: Reparixin can attenuate inflammatory responses in various injury models. In spontaneously hypertensive rats, it effectively decreases systolic blood pressure and increases blood flow, and significantly reduces the thoracic aorta wall thickness. In mouse models of LPS - induced pulmonary inflammation and acid - induced acute lung injury, it shows therapeutic potential, which may be related to its inhibition of CXCR2 - mediated neutrophil recruitment and vascular permeability regulation. Intravital microscopy of the cremaster muscle in mice was performed to assess leukocyte arrest, and the results showed that Reparixin can specifically act on mouse CXCR2 in vivo [1, 3]

L1.2 Cell suspension (1.5-3×10⁶ cells/mL) is then seeded in triplicate in the upper compartment of the chemotactic chamber after being incubated for 15 min at 37°C with either vehicle or Reparixin (1 nM-1μM). The following concentrations of various agonists are seeded in the chamber's lower compartment: 1 nM CXCL8, 0.03 nM fMLP, 10 nM CXCL1, 2.5 nM CCL2, and 30 nM C5a. The chemotactic chamber is incubated for 45 minutes (human PMNs) or 2 hours (monocytes) at 37°C in air with 5% CO₂. After the incubation period, the filter is taken out, cleaned, and stained. Five oil immersion fields are counted for each migration at a high magnification of 100×, following sample coding. Transwell filters with a pore size of 5 μm are used to assess L1.2 migration.

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The cell - based experiment is mainly the study of neutrophil migration and activation: Isolate mouse and human neutrophils, add CXCL8 as a stimulus, and then add different concentrations of Reparixin. Observe neutrophil migration through transwell experiments. Detect the activation of neutrophils by measuring intracellular free calcium concentration, elastase release, production of reactive oxygen intermediates and phosphorylation of downstream signalling molecules. The results show that Reparixin can inhibit the above - mentioned indicators related to neutrophil activation [1, 3]

Rats: There were five SHR (SHR-R) in the Reparixin-treated group, and as controls, there were the same numbers of WKY (WKY-N) and normal saline-treated SHR (SHR-N). Reparixin (5 mg/kg) was injected subcutaneously once daily for three weeks to 18-week-old SHR. Before treatment, and then every week until one week following the last injection, the effects of reparixin on blood flow, blood pressure, and body weight are measured. One week after the last injection, Reparixin's impact on nitric oxide (NO) plasma levels and the expression of mediators related to hypertension in thoracic aortas is investigated.
Mice: There are C57BL/6J mice (20–25 g, 8–10 weeks old). Half an hour prior to the induction of cerebral ischemia, Reparixin (30 mg/kg) is subcutaneously administered. Three distinct experimental groups are created from the animals: Sham (the group where the middle cerebral artery is not occluded but the arteries are visible), Vehicle and Reparixin are the groups that were pre-treated with the drug (i.e., the group that received phosphate buffer solution 60 minutes prior to MCAo) and the vehicle. The animals are evaluated 24 hours after reperfusion using the SHIRPA battery to determine any neurological signs secondary to MCAo.

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- Treatment of Spontaneously Hypertensive Rats: Divide spontaneously hypertensive rats into a Reparixin treatment group and a normal saline control group. Dissolve Reparixin in an appropriate solvent and administer it to the treatment group rats, with a specific administration route and frequency not described in the literature. After a certain period of treatment, measure the systolic blood pressure, blood flow, and observe the thoracic aorta wall thickness [1]
- Treatment of Mouse Lung Injury Models: For LPS - induced pulmonary inflammation and acid - induced acute lung injury models in mice, dissolve Reparixin in an appropriate solvent. Administer it to mice before or after inducing injury, with the administration route possibly being intravenous or intraperitoneal injection (not clearly described in the literature). In the LPS model, observe neutrophil recruitment and vascular permeability; in the acid - induced injury model, measure arterial oxygen partial pressure and other functional parameters. Use intravital microscopy of the cremaster muscle to assess the effect of Reparixin on mouse CXCR2 in vivo by observing leukocyte arrest [3]

[1]. Biol Pharm Bull . 2011;34(1):120-7.

[2]. Br J Pharmacol . 2008 Oct;155(3):357-64.

[3]. Proc Natl Acad Sci U S A . 2004 Aug 10;101(32):11791-6.

Reparixin is a monoterpenoid.
Reparixin has been used in trials studying the treatment and prevention of Breast Cancer, Metastatic Breast Cancer, Pancreatectomy for Chronic Pancreatitis, Islet Transplantation in Diabetes Mellitus Type 1, and Pancreatic Islet Transplantation in Type 1 Diabetes Mellitus.
Reparixin is an orally available inhibitor of CXC chemokine receptor types 1 (CXCR1) and 2 (CXCR2), with potential antineoplastic activity. Upon administration, reparixin allosterically binds to CXCR1 and prevents CXCR1 activation by its ligand interleukin 8 (IL-8 or CXCL8). This may cause cancer stem cell (CSC) apoptosis and may inhibit tumor cell progression and metastasis. CXCR1, overexpressed on CSCs, plays a key role in CSC survival and the ability of CSC to self-renew; it is also linked to tumor resistance to chemotherapy. Inhibition of the IL-8/CXCR1 interaction also potentiates the cytotoxic effect of chemotherapeutic agents. In addition, reparixin inhibits CXCR2 activation and may reduce both neutrophil recruitment and vascular permeability during inflammation or injury.

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Drug Indication
Treatment of Coronavirus disease 2019 (COVID-19)
Treatment of coronavirus disease 2019 (COVID-2019)
Prevention of graft rejection

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The chemokine CXC ligand 8 (CXCL8)/IL-8 and related agonists recruit and activate polymorphonuclear cells by binding the CXC chemokine receptor 1 (CXCR1) and CXCR2. Here we characterize the unique mode of action of a small-molecule inhibitor (Repertaxin) of CXCR1 and CXCR2. Structural and biochemical data are consistent with a noncompetitive allosteric mode of interaction between CXCR1 and Repertaxin, which, by locking CXCR1 in an inactive conformation, prevents signaling. Repertaxin is an effective inhibitor of polymorphonuclear cell recruitment in vivo and protects organs against reperfusion injury. Targeting the Repertaxin interaction site of CXCR1 represents a general strategy to modulate the activity of chemoattractant receptors.[3]

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Background and purpose: Acute lung injury (ALI) remains a major challenge in critical care medicine. Both neutrophils and chemokines have been proposed as key components in the development of ALI. The main chemokine receptor on neutrophils is CXCR2, which regulates neutrophil recruitment and vascular permeability, but no small molecule CXCR2 inhibitor has been demonstrated to be effective in ALI or animal models of ALI. To investigate the functional relevance of the CXCR2 inhibitor Reparixin in vivo, we determined its effects in two models of ALI, induced by either lipopolysaccharide (LPS) inhalation or acid instillation. Experimental approach: In two ALI models in mice, we measured vascular permeability by Evans blue and evaluated neutrophil recruitment into the lung vasculature, interstitium and airspace by flow cytometry. [2]

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- Mechanism of Action: Reparixin acts by non - competitively blocking the activation of CXCR1 and CXCR2 receptors, inhibiting intracellular signal pathways without affecting receptor bindings, and thus interfering with the biological effects mediated by CXCL8, such as neutrophil migration and activation - related inflammatory responses [1, 3]
- Indications: It may be used for the treatment of inflammatory diseases related to neutrophil migration, such as hypertension - related vascular inflammation and acute lung injury, but there is no clear indication of FDA - approved indications in the literature [1, 3]

C14H21NO3S

283.39

283.124

C, 59.34; H, 7.47; N, 4.94; O, 16.94; S, 11.31

266359-83-5

(Rac)-Reparixin; 957407-64-6; Reparixin L-lysine salt; 266359-93-7

9838712

White to off-white solid powder

1.137g/cm3

103-105 ºC

1.524

3.985

1

3

5

19

389

1

S(C([H])([H])[H])(N([H])C([C@]([H])(C([H])([H])[H])C1C([H])=C([H])C(=C([H])C=1[H])C([H])([H])C([H])(C([H])([H])[H])C([H])([H])[H])=O)(=O)=O

KQDRVXQXKZXMHP-LLVKDONJSA-N

InChI=1S/C14H21NO3S/c1-10(2)9-12-5-7-13(8-6-12)11(3)14(16)15-19(4,17)18/h5-8,10-11H,9H2,1-4H3,(H,15,16)/t11-/m1/s1

(2R)-2-[4-(2-methylpropyl)phenyl]-N-methylsulfonylpropanamide

2934.99.9001

Powder      -20°C    3 years

                     4°C     2 years

In solvent   -80°C    6 months

                  -20°C    1 month

Room temperature (This product is stable at ambient temperature for a few days during ordinary shipping and time spent in Customs)

Solubility in Formulation 1: ≥ 2.5 mg/mL (8.82 mM) (saturation unknown) in 10% DMSO + 40% PEG300 + 5% Tween80 + 45% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 400 μL PEG300 and mix evenly; then add 50 μL Tween-80 to the above solution and mix evenly; then add 450 μL normal saline to adjust the volume to 1 mL.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 2: ≥ 2.5 mg/mL (8.82 mM) (saturation unknown) in 10% DMSO + 90% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of 20% SBE-β-CD physiological saline solution and mix evenly.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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Solubility in Formulation 3: ≥ 2.5 mg/mL (8.82 mM) (saturation unknown) in 10% DMSO + 90% Corn Oil (add these co-solvents sequentially from left to right, and one by one), clear solution.
For example, if 1 mL of working solution is to be prepared, you can add 100 μL of 25.0 mg/mL clear DMSO stock solution to 900 μL of corn oil and mix evenly.

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Solubility in Formulation 4: ≥ 2.5 mg/mL (8.82 mM) (saturation unknown) in 5% DMSO + 40% PEG300 + 5% Tween80 + 50% Saline (add these co-solvents sequentially from left to right, and one by one), clear solution.
Preparation of saline: Dissolve 0.9 g of sodium chloride in 100 mL ddH₂ O to obtain a clear solution.

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Solubility in Formulation 5: 2.5 mg/mL (8.82 mM) in 5% DMSO + 95% (20% SBE-β-CD in Saline) (add these co-solvents sequentially from left to right, and one by one), suspension solution; with ultrasonication.
Preparation of 20% SBE-β-CD in Saline (4°C，1 week): Dissolve 2 g SBE-β-CD in 10 mL saline to obtain a clear solution.

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 (Please use freshly prepared in vivo formulations for optimal results.)